When it comes to property damage, floods are the most costly natural disaster in Canada. While thousands of Canadians have been affected by washed-out roads, downed power lines and rising water levels, for many others, the risk is more personal. In fact, it's beneath their feet.

According to the Canada
Mortgage and Housing Corporation, or CMHC, insurance claims
for basement floods are estimated to cost $140 million each year.
This represents approximately 40,000 reported cases of basement
flooding with damage averaging between $3,000 and $5,000 per incident.

While a basement flood can be unexpected and traumatic,
there are steps you can take to lessen the impact on your home and
prevent future flooding.

Plumbing 101
To safeguard your home, it's important to know a bit about basic street-level plumbing and drainage. Typically, the sanitary sewer is a pipe that transports wastewater from your home. This includes water from sanitary fixtures such as toilets and sinks, floor drains and may include groundwater from weeping tiles around your home's foundation.

A storm sewer is a larger pipe that carries storm water runoff. Runoff from the roof of your house should flow through the downspout, via the eavestroughs, and into the storm sewer. If any of these systems fail, you've got the makings of a basement flood.

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Causes of flooding
Heavy rainfall, a rapid spring thaw or a river swell can cause storm
sewers to overflow into the sanitary sewer and cause a back-up.
Alternatively, tree roots, debris such as grease, paper or other
foreign objects or a pipe collapse may cause a blockage in the pipe
leading from your home to the street sewer main.

Burst pipes, leaky water heaters or old laundry hoses can also discharge water directly into your basement. Even poor lot drainage, plugged downspouts and foundation cracks or leaks can create a slow but steady flood of water.

Cleaning up
While the loss of furniture, equipment or family treasures can be
devastating, a flood can have far reaching consequences long after
the last of the water has been mopped up.

"Depending on the type of water and the growing
conditions, you can have mould growing anywhere between 24 to 72
hours (after a flood)," says Phil Moore, vice-president of
sales and marketing for the restoration and remediation company
Disaster Kleenup Canada, based in Mississauga, Ont. "If you
have sensitive people in the home -- elderly, newborn or those with
compromised immune systems -- they can be exposed to a major problem."

Not only can mould be a significant health threat, but over time, it can cause structural damage to buildings and depreciate the value of your home. What's more, mould spores can spread.

"Quick action is really required for everyone's benefit," says Don Fugler, senior researcher, policy and research division, at the CMHC. "The more you delay, the more chance you have of incredibly high costs of remediation."

As soon as you discover water, contact your insurance
company and your municipality, especially if you suspect a sewer
backup (the water will appear grey rather than clear).